[Python] String comparison on pyarrow/table.pxi should require the GIL

[raulcd]

Describe the bug, including details regarding any error messages, version, and platform.

As per discussion here string comparison should require the GIL:
We should modify this:

    with nogil:
        options.unify_schemas = promote_options != "none"
        ...

to

    options.unify_schemas = promote_options != "none"
    with nogil:
        ...

Component(s)

Python